1. Field of the Invention
The present invention is related to a digital electric power inverter, and especially to a DC to AC power inverter particularly suitable to be used as a protection circuit module structure to protect the elements of the power inverter from being damaged and to be able to provide the actuating power for a machine.
2. Description of the Prior Art
As shown in FIG. 1, heavy tool machines in the markets consume huge electric power when in actuating, if such a machine is to be actuated, several folds of monetary amount must be paid to purchase an electric power inverter with several folds of functional specification for actuating a small machine. For example, a sand wheel needs 200W for running, while the transient power for actuating is over 1000W; therefore, in using such a machine, an electric power inverter of 1000W must be purchased. The reason is that, a conventional electric power inverter triggers a protecting loop to shut outputting in corresponding to the detecting signal from a detecting loop when the output terminal is given a heavy load, to thereby protect the interior electronic elements; this is because that conventional designing has to trigger a protecting line according to the detecting of the output state to turn off the system to protect the product.
And a conventional electric power inverter may render the internal detecting loop thereof to mistake a case for a loading short circuit, in which case, the output terminal thereof is connected with an inductive load or in actuating a load with a larger current; thereby, a protection loop is triggered to shut outputting, to in turn make a machine not work. This is an unsolvable problem and technical bottleneck of the conventional electric power inverter in that it is unable to distinguish a short circuit from an inductive load.
In conventional designing, PWM (pulse width modulation) mostly adopts the driving mode of IC outputting; if a relatively inexpensive IC is used, the designing will be more difficult or even the specification must be degraded. For example, when a PWM converting signal has an inadequate duty and makes a larger temperature rising, the frequency must be adjusted down or the IC shall be changed to effectively improve the case.
Therefore, the motive of the present invention is to improve the conventional electric power inverters to get rid of the above stated defects, and to provide a digital electric power inverter which sufficiently uses the control character of a CPU (a microcomputer) to similarly provide a load with an output power, but the CPU turns off output in time before the output power makes the elements crumbled, in order that the elements can restore their functions; a short time after restoration, the CPU turns on output again, till it once more turns off before the elements are crumbled. The process is repeated again and again to protect the elements from being damaged, and the actuating power for a machine can be provided; this can take the place of the function of a conventional IC, and can make a large improvement in saving the cost of man work and the fineness of products.
The primary object of the present invention is to provide an accurately controlling digital electric power inverter with parts able to develop their largest effects.
To achieve the above stated object, the present invention is comprised of a CPU, a PWM driving circuit, a PWM converting circuit, a rectifying circuit, an AC driving circuit, a DC/AC inverting circuit, a plurality of detecting circuits and an alarm circuit. The present invention is characterized by that: the entire circuitry thereof is designed to be controlled by the CPU that can accurately control these circuits to endue the power inverter with an intact and multi-selection protecting function, thus to render the parts thereof to develop their largest effects.